Here's what I did to get a start. First I did my research to decide what mechanicals I wanted to install. Part of that was the dimensional issues of where and if it will fit. Secondly to get the specs for amp rating to determine wire size.
I then did a list, by "room" to get an over all feel where loads would be. Note: I ran most of my circuits as separate dedicated runs. I only paired up some lighting (in the same 'room' and a couple 110v plugs. Of course all lighting is led.
I also determined that some circuits would be shore power only circuits since I knew I would not attempt to run some things off the batteries (AC, microwave (if I ever install one), circuit for frig (dual electric 12&120).
Here's my list to give you an idea of what I wanted to be able to reference as plans and work proceeded.
Because we were doing a vintage 58 and retaining the majority of the original cabinets and using original appliances with updated mechanicals I wanted to bury a lot of the wiring in the belly pan to minimize modifying cabinets. The junction boxes are open through the subfloor and buried in the cabinets/beds/banquette.
If you decide to do this suggest going to 1.5 or 2" pvc conduit. I used 1" and bringing all that wiring to a main box gets cramped.
With a lot of electronics to install we decided to take advantage of the old wall panel heater face and hide it there. The new ducted furnace is under the kitchen sink.
I also ran aluminum fuel tubing (5/8") through the wall and ceiling to get wiring to needed areas to make sure an future repairs/upgrades could be easily done without removing interior walls.
Hope this helps you sort out your rejuvenation.